Alex rider - what happened?

Chapter 10

Alex was fiddling with his black belt absentmindedly as Yassen drove to the address Alex gave him.
Alex walked into the room and someone rushed towards him trying to land a punch. Alex grabbed the outstretched arm after he dodged and flipped the person over before dodging a roundhouse kick and swiping the other person's leg away from her, causing her to lose balance. The two kids on the ground groaned as they quickly rolled into a sitting position. "Sempai is so hard to beat!" The girl whined. [sempai means senior in Japanese.]
Alex smiled as he sat down at a chair and started reading waiting for the instructor to come as it was still early. 6 students had already arrived, including the two that tried to beat Alex. Yassen watched the encounter quietly behind the students. "Why are you reading such a thick book?"
"A friend wanted me to read it." Alex said, remembering Cassandra chucking the book at him and ordering him to read it. Storm glass by Maria V. Snyder.
"I wanna be a spy. " A boy whined. Yassen watched with more interest now as Alex seem to tense up and his eyes snap up towards the boy with careful pretend interest. "A man came earlier, saying that they are considering to hire us to be spies." Blunt. Alex snapped the book shut and lowered the book onto his lap. "Spying is boring. All you do is wait. And wait. And wait. And wait. Nothing more. It's boring. But even without doing anything, you could be killed."
The students shrieked. "We're too young to die!" Something flashed in Alex's eyes as he remembered the first mission. Herod Sayle had said you're never too young to die. "How about I test you guys. If you guys pass this test, you guys are deemed worthy of becoming a spy and I'll even teach you guys a few tricks." Alex said, knowing the kids wouldn't diminish all hopes until it has been proven. "Okay!" The kids said chirpily. "What is different in this room, find it and tell me." The kids went around looking for what is different, making a lot of noise and moving a lot of things. "Nothing is." They all said. "You all didn't pass. One, a spy never makes noise. You guys caused a racket. Two, a spy never moves thing out of place without having them put back into the exact spot. You guys moved a lot things around. Three, a spy notices his surroundings. There is one more extra person in the room which you guys failed to notice." Alex said as he gestured to Yassen who was sitting in the corner of the room, observing. He raised a hand as a greeting. Alex felt a migraine knocking on his door and a wave of dizziness from not eating sweep through him. "I'm going out. I'll be back." Alex said as he stood up, bringing his wallet and phone with him.